Biometric authentication has been known as a technique to identify an individual person based on biological characteristics which is possessed by a human being, such as the vein pattern, the face pattern and the like. In the biometric authentication, first, data representing the biological characteristics of an authentication target is registered as a registered template, and the subject person is identified by comparing authentication data representing characteristics of the biological pattern of an individual person obtained by a sensor such as a camera with the registered template in the authentication. Specifically, the degree of similarity between the authentication data and the registered template is calculated, and when the degree of similarity exceeds a predetermined threshold, the authentication target is determined as the subject person. In such biometric authentication, the authentication errors occur at a certain rate. As one of the authentication errors, there is a false rejection error by which, even though a characteristic data indicates the subject person, identity verification may fail due to a low degree of similarity of the characteristic data with the registered template.
There are mainly two possible reasons for the authentication errors described above. One reason is ascribed to the posture mismatch of the authentication part with the direction of the sensor used to the authentication. Since the subject of the authentication is a human being, the authentication part is not necessarily captured by the sensor when a posture of the authentication part matches with the posture in the registered template. Another reason is ascribed to an external light on the biometric authentication apparatus. The biometric authentication using an image is sometimes affected by the sunlight from outside, indoor incandescent lights and the like. While many of the authentication apparatuses illuminate the subject using a light source provided for themselves and capture the image, when the amount of unintended light from the sunlight and incandescent lights has a large influence on the image, these external lights cause an authentication error.
However, since it is difficult to save authentication data including data of the face and veins of a person to be authenticated as a log due to security and privacy issues, it is difficult for the administrator of the biometric authentication apparatus to investigate the cause of the occurrence of an authentication error.